ARM: dts: aspeed: tiogapass: Add uarts for SoL

Added uart2 and uart3 in Facebook Tiogapass for routing serial input
from Host to BMC for SoL via LPC.

Signed-off-by: Vijay Khemka <vijaykhemka@fb.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>